Synthesis and processes of core shell impact modifiers and impact modified thermoplastic compositions are well known.
The document U.S. Pat. No. 5,514,772 describes a method for producing powdery and granular polymers. The method includes two coagulation steps: coagulating a latex of the polymer, the latex containing a sulfuric acid ester series and/or sulfonic acid series anionic surface active agents, with an acid to an amount of the polymer of 40 to 80 weight percent at a first coagulation step, and then bringing coagulation to completion with an acid or salt at a second coagulation step. A powder with a sharp particle size distribution is obtained. The process described involves four vessels and the pH is always below 3.
The document U.S. Pat. No. 4,897,462 describes a slow coagulation process in a pH range from 2 to 6 during the coagulation, followed by a fast completion of the coagulation at a pH<2, in order to obtain a spherical powder without fine particles. This slow coagulation is achieved due to addition of salt in diluted concentrations meaning a large amount of water.
WO2006/057777 describes the synthesis of core-shell MBS particles by emulsion graft polymerization. The polymer particles are coagulated with sulfuric acid and further heated up to 85° C.
WO 2009/126637 describes functional MBS impact modifiers synthesized by a multistage emulsion polymerization. At the end the reaction mixture obtained is coagulated in order to separate the polymer. The coagulating treatment is performed by bringing into contact the reaction mixture with a saline solution (calcium chloride or aluminum chloride —CaCl2 or AlCl3) or a solution acidified with concentrated sulfuric acid and then to separate, by filtration, the solid product resulting from the coagulating, the solid product then being washed and dried to give a graft copolymer as a powder.
The document EP 0900 827 describes emulsion grafted polymers, and especially MBS core-shell polymers. Which are substantially, free from components that degrade the thermoplastic polymer, in that case polycarbonate. Therefore such components are omitted during the synthesis. More generally in order to increase the thermal stability of the impact modified polycarbonate any basic compound has to avoided during the synthesis of the impact modifier. It is especially insisted on the use of a certain class of surfactants during the emulsion polymerization, especially sulfate- and sulfonate-containing surfactants.
All prior art is generally silent about such process details of synthesis of the core-shell impact modifier especially its pH at the end of the synthesis, the pH before and during the recovery process and choice of electrolyte and the performance of such an impact modifier in a thermoplastic composition.